1. Department of Mechanical and Aerospace Engineering, and Organic and Carbon Electronics Laboratories (ORaCEL), North Carolina State University, Raleigh, North Carolina 27695, United States
2. Department of Materials Science and Engineering, and Organic and Carbon Electronics Laboratories (ORaCEL), North Carolina State University, Raleigh, North Carolina 27695, United States
3. Department of Physics, and Organic and Carbon Electronics Laboratories (ORaCEL), North Carolina State University, Raleigh, North Carolina 27695, United States
4. Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, United States
5. School of Materials Science and Engineering, Tianjin University, Tianjin 300072, P. R. China